1. Field of the Invention
The present invention relates to plasma discharge devices. More particularly, the present invention relates to devices for propagating a plasma discharge along a prescribed path. Still more particularly, the present invention relates to planar plasma discharge shift register apparatus and circuitry for controlling the same.
2. Prior Art
Although plasma discharge cells have found increased use in recent years in display applications, such use has primarily involved the use of 2-dimensional matrix arrays constituting a plasma panel. Such plasma panels, described, for example, in U.S. Pat Nos. 3,559,190 issued to D. L. Bitzer et al, on Jan. 26, 1971, and 3,499,167 issued to T. C. Baker et al on Mar. 3, 1970, typically operate in a half-select mode in response to signals applied on horizontal and vertical addressing electrodes. While such panels are appropriate for many applications, their relatively complicated structure and extensive drive circuitry give rise to complexity and expense not justified for many applications.
One attempt to provide for simpler plasma discharge display devices involves the use of devices for propagating a plasma discharge in a manner analogous to information transfer by electrical signals in shift register circuits. Thus, for example, U.S. Pat. Nos. 3,781,600 issued to W. E. Coleman et al on Dec. 25, 1973; 3,775,764 issued to J. P. Gaur on Nov. 27, 1973; and 3,795,908 issued to A. W. McDowell et al on Mar. 5, 1974 describe such devices. Each of the above-cited shift register structures has in common with the earlier-mentioned plasma panel arrangements the characteristic that plasma discharge control electrodes are disposed on opposite sides of a gas volume by providing a "sandwich" of separate glass substrates separated by glass or other dielectric structures. Such arrangements suffer from the limitation tht the gas discharge occurs between the electrodes and is therefore at least partly obscured by the electrodes themselves. This is true even in those cases where nominally transparent conductors are used. Further, the need for precise registration of opposing electrodes imposes strict tolerances on the sandwich elements.
In U.S. Pat. No. 3,798,502 issued on Mar. 19, 1974 to P. D. Ngo, there is disclosed an essentially planar structure including a plurality of plasma discharge cells in a shift register configuration. Because all electrodes are deposited by thick film or equivalent techniques on a single substrate, the entire glow discharge is available for direct viewing.